Two-wheel castor for a chair or the like

ABSTRACT

A two-wheel castor, especially for a chair or a similar piece of furniture, consisting of a supporting member which is adapted to be mounted on the chair or the like and to support two wheels. The supporting member and the wheels are partly surrounded by a casing which is shaped like the periphery of a solid of revolution, e.g. a ball socket, which has an opening which is smaller than a diametrical cross-section, so that the wheels are well protected. The supporting member has a peripheral surface the shape of which corresponds to the shape of the inner surface of the casing. Thereby the supporting member can be mounted in the casing and kept in position without any latch means, and by a suitable dimensioning of the parts the wheels and the supporting member can be inserted in the casing through the opening in the casing.

United States Patent n 1 Andersen Dec. 2, 1975 TWO-WHEEL CASTOR FOR ACHAIR OR THE LIKE [76] Inventor: Jens Peter Andersen, Jernbanealle [30]Foreign Application Priority Data Primary E.raminer-Paul R. GilliamAssistant Examiner-Doris L. Troutman Attorney, Agent, or Firm-Ladas,Parry, Von Gehr, Goldsmith 8L Deschamps [57] ABSTRACT A two-wheelcastor, especially for a chair or a similar piece of furniture,consisting of a supporting member which is adapted to be mounted on thechair or the like and to support two wheels. The supporting member andthe wheels are partly surrounded by a casing which is shaped like theperiphery of a solid of revolution, e.g. a ball socket, which has anopening which is smaller than a diametrical cross-section, so that thewheels are well protected. The supporting member has a peripheralsurface the shape of which corresponds to the shape of the inner surfaceof the casing. Thereby the supporting member can be mounted in thecasing and kept in position without any latch means, and by a suitabledimensioning of the parts the wheels and the supporting member can beinserted in the casing through the opening in the casing.

5 Claims, 6 Drawing Figures US. Patent Dec. 2, 1975 TWO-WHEEL CASTOR FORA CHAIR OR THE LIKE This invention relates to a castor, especially for achair, of the type which has a disc-shaped supporting member which issubstantially vertical in the operative position and which is rotatablymounted on asubstantially vertical shaft member which is mounted'on thechair or the like, from each side surface of which supporting member ashaft pin extends, on each shaft pin a wheel being journalled, saidsupporting member and a portion of the wheels being surrounded by acasing which is open at the bottom, the shaft which connects thesupporting member with the chair or the like extending through anopening in said casing.

A castor construction is known in which the casing consists of a portionof a cylinder surface without end walls, so that the wheels can bemounted on the shaft pins by insertion from the side. Each wheel has aboss with a groove in which a latch member engages, which latch memberis mounted on the supporting member by means of a screw.

The castor according to this invention is characterised in that thecasing is shaped as the periphery of a solid of revolution which at thebottom has an opening which is smaller than the largest cross-sectionarea of the casing, and that the supporting member has a peripheralsurface the shape of which corresponds to the shape of the inner surfaceof the casing.

With this construction of the castor a casing may be used whichsurrounds a rather large portion of the wheels, so that the wheels arewell protected, and in spite of this fact the castor can be assembledwithout using any latch means, as the supporting member, when it ispositioned in such a way that its peripheral surface corresponding tothe shape of the casing abuts the inner side of the casing, is kept inthis position only by means of the shaft pin which connects the castorto the chair or the like, and the castor according to this constructiononly consists of parts which are important for the function, viz. thesupporting member, the casing, the shaft pins, the wheels, and the shaftpin which connects the castor to the chair or the like. Special latchmeans which make the castor expensive and make the assembly of thecastor complicated and further provide a risk of unintentional takingapart of the castor are eliminated.

Some embodiments of the invention are described in the following withreference to the drawing, where FIG. 1 is a sectional view of a castoraccording to the invention,

FIG. 2 a section along the line II-II in FIG; 1,

FIG. 3 the same as FIG. 1 for a modified embodiment,

FIG. 4 a section along the line IV--IV in FIG. 3,

FIG. 5 the same as FIG. 1 for a further modification, and

FIG. 6 a cross-section along the line VI-VI in FIG. 5.

The castor which is shown in FIGS. 1 and 2 consists ofa disc-shapedsupporting member 1 the periphery of which is constituted by a circularportion 2 and a cord 3 in the circle. The arched surface 3 correspondingto the circular portion is shaped as a part of a ball zone. As shown inFIG. 1, the supporting member 1 has a larger width at the top than atthe bottom, so that the shape of the member is like an extended ballsector. In

the supporting member there are three vertical bores 4 of which themiddle bore is positioned in the vertical middle axis of the supportingmember, as shown in FIG. 2. The three bores 4 are adapted to receive ashaft pin (not shown) connecting the castor with a chair or the like. Inthe bore to the right in FIG. 2 a sleeve 5 is mounted, and in thissleeve the said shaft pin is rotatably mounted, so that the castor as aunit can swing about the said shaft pin. The three bores can be usedoptionally, and if two shaft pins are used, the castor will be fixed tothe chair or the like.

In the supporting member 1 two shaft pins 6 are mounted under an obtuseangle to each other, as shown in FIG. 1. On the shafts two wheels 7 arerotatably mounted. Each wheel has such a shape that its peripheralportion 8 can run on the floor on which the chair or the like ispositioned.

The supporting member and the wheels are surrounded by a casing 9 whichis shaped as a ball socket having the same radius as the peripheralsurface 3 of the supporting member 1. The casing has an opening 10 whichis constituted by a substantially horizontal plane cutting removing aball segment, so that the edge of the opening 10 is circulanAs shown inFIG. 2, the sleeve 5 passes through the casing, and thereby the easingis fixed in relation to the supporting member 1.

The castor according to FIGS. 1 and 2 is taken apart thereby that thesleeve 5 and the shaft pin (not shown) are removed from the supportingmember 1, whereafter the supporting member 1 is rotated about the axis11 in FIG. 2, so that one of the wheels 7 is positioned at the opening10. Now, this wheel can be removed together with the shaft pin 6 throughthe opening 10 in the casing. Thereafter the supporting member 1 isrotated in opposite direction about the axis 11 until the second wheel 7is positioned at the opening 10, and now, this wheel and its shaft pin 6can be removed from the supporting member 1. At last the supportingmember is rotated about the axis 11 to the position shown in FIG. 1, andthereafter it is rotated about the axis 12 until the cord 3' issubstantially vertical, whereafter the supporting member 1 can beremoved through the opening 10. The assembly of the parts takes place inthe same manner as described, but in opposite order, and no speciallatch means are used. The supporting member 1 is fixed in relation tothe casing 9 by means of the shaft pin which connects the castor withthe chair or the like and which is not shown in the drawing. As willappear from FIG. 1, the wheels 7 and the shaft pins 6 cannot changeposition or fall out from the easmg.

In the embodiment according to FIGS. 3 and 4 the casing 13 is shaped asa part of a cylinder surface 13' and has two plane end walls 14. Theopening 10 is limited by two cords in the circular end walls 14 and twogeneratrices in the cylinder surface. The supporting member 15 is shapedas a disc having equal thickness and a periphery which is constituted byan arched surface corresponding to the inner surface of the casing and acord 3'. The shaft pins for the wheels 7 consist of a common shaft 16which is coaxial with the axis of the casing and has substantially thesame length as the distance between the end walls 14.

The diameter of the wheels is less than the distance between the twosaid generatrices, so that the wheels can pass the opening 10. Thecastor is taken apart thereby that the supporting member 15 afterremoval of the shaft pin which connects the castor with the chair or thelike is rotated about the axis of the shaft 16, whereafter the completeunit consisting of the supporting member 15, the shaft 16, and thewheels 7 can be drawn through the opening 10.

The castor according to FIGS. 5 and 6 has in the same way as the castoraccording to FIGS. 1 and 2 a casing 3 which is a ball socket, and thesupporting member 17 has the same shape as the supporting member l withthe only difference that it has an equal thickness. The wheels 7 aremounted on a common shaft 16 the axis of which coincides with a diameterin the ball socket. This castor is assembled and taken apart in the samemanner as the castor according to FIGS. 1 and 2.

As the shaft 16 has the same length as a diameter in the ball socket theinner surface of the ball socket can constitute stop means for the endsof the shaft, and as shown in FIG. 5, it can also constitute stop meansfor the wheels 7.

The supporting member 17 may be provided with a slot 18 connecting thebore for the shaft 16 with the straight edge 3, which is shown by thestippled line in FIG. 6. Thereby it will be possible to mount the wheels7 and the shaft 16 in the casing and thereafter to insert the supportingmember in the casing.

Known castors have a supporting member which is integral with thecasing, and this unit is manufactured by a moulding process. Accordingto this invention the casing can be manufactured separately, e.g. bydeformation of a plate material, such as steel plate, and it is notnecessary that the supporting member is of the same material as thecasing.

I claim:

1. An improved two-wheel castor for a chair or the like having shaftmeans extending downwardly therefrom, comprising casing means having ahole therein through which said shaft means can be downwardly inserted,and wheel supporting means within said casing means, said wheelsupporting means having a hole therein for receiving said downwardlyinserted shaft means and having a central bore, pin means inserted intosaid bore and two opposed wheels mounted on said pin means, at oppositesides of the wheel supporting means,

wherein the improvement comprises the combination of the followingfurther features:

i. the casing means is a hollow casing adapted to enclose the majorportion of said two wheels, the interior of which is shaped tocorrespond with the curved surface of a segment of a solid of revolutionabout an axis extending parallel to the chordal plane of said segment,said casing having an opening at the bottom thereof corresponding tosaid chordal plane;

. the wheel supporting means is a separate member in the form of asegment of a disc, the radius of the curved portion of the periphery ofthe disc corresponding to the maximum radius of said solid of revolutionand the perpendicular height from the center of the chord of the discsegment to said curved portion of the periphery of the disc beinggreater than the radius of said curved portion but smaller than themaximum dimension of said opening at the bottom of the casing;

whereby to assemble the castor said separate wheel supporting memberhaving the two wheels mounted thereon are inserted through the openingat the bottom of the casing and then turned until the holes in thecasing and the wheel supporting means are in registration to permitdownward insertion of said shaft means extending from the chair or thelike, the castor being disassembled by retracting said shaft means andturning the wheel supporting member until it is removable through saidopening.

2. A castor according to claim 1 in which sleeves are provided extendinginto said bores in the supporting member through corresponding holes inthe upper portion of the casing, for receiving said pin means.

3. A castor according to claim 1 in which the inner surface of thecasing is spherical and the shaft pin means comprises two pins mountedat an obtuse angle to each other, each having an end extending into saidcentral hole in the supporting means, and each having a wheel mountedthereon and shaped to conform with said spherical surface.

4. A castor according to claim 1 in which the inner surface of thecasing is spherical and the shaft pin means comprises a single pinextending through said central hole in the supporting means, and havinga wheel mounted at each end thereof and shaped to conform with saidspherical surface.

5. A castor according to claim 1 in which the inner surface of thecasing is a circular cylinder with two plane end walls and the shaft pinmeans comprises a single pin extending through said central hole in thesupporting means, and having a wheel mounted at each end thereof andshaped to conform with said plane end walls.

1. An improved two-wheel castor for a chair or the like having shaftmeans extending downwardly therefrom, comprising casing means having ahole therein through which said shaft means can be downwardly inserted,and wheel supporting means within said casing means, said wheelsupporting means having a hole therein for receiving said downwardlyinserted shaft means and having a central bore, pin means inserted intosaid bore and two opposed wheels mounted on said pin means, at oppositesides of the wheel supporting means, wherein the improvement comprisesthe combination of the following further features: i. the casing meansis a hollow casing adapted to enclose the major portion of said twowheels, the interior of which is shaped to correspond with the curvedsurface of a segment of a solid of revolution about an axis extendingparallel to the chordal plane of said segment, said casing having anopening at the bottom thereof corresponding to said chordal plane; ii.the wheel supporting means is a separate member in the form of a segmentof a disc, the radius of the curved portion of the periphery of the disccorresponding to the maximum radius of said solid of revolution and theperpendicular height from the center of the chord of the disc segment tosaid curved portion of the periphery of the disc being greater than theradius of said curved portion but smaller than the maximum dimension ofsaid opening at the bottom of the casing; whereby to assemble the castorsaid separate wheel supporting member having the two wheels mountedthereon are inserted through the opening at the bottom of the casing andthen turned until the holes in the casing and the wheel supporting meansare in registration to permit downward insertion of said shaft meansextending from the chair or the like, the castor being disassembled byretracting said shaft means and turning the wheel supporting memberuntil it is removable through said opening.
 2. A castor according toclaim 1 in which sleeves are provided extending into said bores in thesupporting member through corresponding holes in the upper portion ofthe casing, for receiving said pin means.
 3. A castor according to claim1 in which the inner surface of the casing iS spherical and the shaftpin means comprises two pins mounted at an obtuse angle to each other,each having an end extending into said central hole in the supportingmeans, and each having a wheel mounted thereon and shaped to conformwith said spherical surface.
 4. A castor according to claim 1 in whichthe inner surface of the casing is spherical and the shaft pin meanscomprises a single pin extending through said central hole in thesupporting means, and having a wheel mounted at each end thereof andshaped to conform with said spherical surface.
 5. A castor according toclaim 1 in which the inner surface of the casing is a circular cylinderwith two plane end walls and the shaft pin means comprises a single pinextending through said central hole in the supporting means, and havinga wheel mounted at each end thereof and shaped to conform with saidplane end walls.